(PHP 7, PHP 8)
random_int — Generates cryptographically secure pseudo-random integers
$min
, int $max
) : intGenerates cryptographic random integers that are suitable for use where unbiased results are critical, such as when shuffling a deck of cards for a poker game.
The sources of randomness used for this function are as follows:
Note: Although this function was added to PHP in PHP 7.0, a » userland implementation is available for PHP 5.2 to 5.6, inclusive.
min
The lowest value to be returned, which must be
PHP_INT_MIN or higher.
max
The highest value to be returned, which must be less than or equal to
PHP_INT_MAX.
Returns a cryptographically secure random integer in the range
min to max, inclusive.
Example #1 random_int() example
<?php
var_dump(random_int(100, 999));
var_dump(random_int(-1000, 0));
?>
以上例程的输出类似于：
int(248) int(-898)
On my system (5th gen i7) random_int() takes about 14x longer to do the same number of calculations than rand().
for ($i=0; $i<10000000; $i++)
$x = rand(1, PHP_INT_MAX);
Takes 0.86 seconds for rand(), 12.29 seconds for random_int(). So use random_int() somewhat sparingly.
If it's not really important to be truly random, use rand() instead, especially in a tight loop.
<?php
// PHP >= 7
function str_rand(int $length = 16){
$x = '';
for($i = 1; $i <= $length; $i++){
$x .= dechex(random_int(0,255));
}
return substr($x, 0, $length);
}
var_dump(str_rand());
?>
Here is a simple backporting function, it works for PHP >= 5.1
<?php
if (!function_exists('random_int')) {
function random_int($min, $max) {
if (!function_exists('mcrypt_create_iv')) {
trigger_error(
'mcrypt must be loaded for random_int to work',
E_USER_WARNING
);
return null;
}
if (!is_int($min) || !is_int($max)) {
trigger_error('$min and $max must be integer values', E_USER_NOTICE);
$min = (int)$min;
$max = (int)$max;
}
if ($min > $max) {
trigger_error('$max can\'t be lesser than $min', E_USER_WARNING);
return null;
}
$range = $counter = $max - $min;
$bits = 1;
while ($counter >>= 1) {
++$bits;
}
$bytes = (int)max(ceil($bits/8), 1);
$bitmask = pow(2, $bits) - 1;
if ($bitmask >= PHP_INT_MAX) {
$bitmask = PHP_INT_MAX;
}
do {
$result = hexdec(
bin2hex(
mcrypt_create_iv($bytes, MCRYPT_DEV_URANDOM)
)
) & $bitmask;
} while ($result > $range);
return $result + $min;
}
}
?>
Randomness test
<?php
$max = 100; // number of random values
$test = 1000000;
$array = array_fill(0, $max, 0);
for ($i = 0; $i < $test; ++$i) {
++$array[random_int(0, $max-1)];
}
function arrayFormatResult(&$item) {
global $test, $max; // try to avoid this nowdays ;)
$perc = ($item/($test/$max))-1;
$item .= ' '. number_format($perc, 4, '.', '') .'%';
}
array_walk($array, 'arrayFormatResult');
print_r($array);
?>
This function is based on Andrew Moore's UUID generation function on the uniqid function; it has been updated to use random_int() on PHP 7.0 or later yet continue to function with earlier versions using mt_rand().
function generateUUIDv4()
{
if(version_compare(PHP_VERSION,'7.0.0', '<') )
{
return sprintf('%04x%04x-%04x-%04x-%04x-%04x%04x%04x',
// 32 bits for "time_low"
mt_rand(0, 0xffff), mt_rand(0, 0xffff),
// 16 bits for "time_mid"
mt_rand(0, 0xffff),
// 16 bits for "time_hi_and_version",
// four most significant bits holds version number 4
mt_rand(0, 0x0fff) | 0x4000,
// 16 bits, 8 bits for "clk_seq_hi_res",
// 8 bits for "clk_seq_low",
// two most significant bits holds zero and one for variant DCE1.1
mt_rand(0, 0x3fff) | 0x8000,
// 48 bits for "node"
mt_rand(0, 0xffff), mt_rand(0, 0xffff), mt_rand(0, 0xffff)
);
}
else
{
return sprintf('%04x%04x-%04x-%04x-%04x-%04x%04x%04x',
// 32 bits for "time_low"
random_int(0, 0xffff), random_int(0, 0xffff),
// 16 bits for "time_mid"
random_int(0, 0xffff),
// 16 bits for "time_hi_and_version",
// four most significant bits holds version number 4
random_int(0, 0x0fff) | 0x4000,
// 16 bits, 8 bits for "clk_seq_hi_res",
// 8 bits for "clk_seq_low",
// two most significant bits holds zero and one for variant DCE1.1
random_int(0, 0x3fff) | 0x8000,
// 48 bits for "node"
random_int(0, 0xffff), random_int(0, 0xffff), random_int(0, 0xffff)
);
}
}